Screening apparatus



July 19, 1966 H. J. DANIELS 3,261,470

SCREENING APPARATUS Filed May 31, 1965 lNVENTOR Herman J. Dqniels aw W 3,261,470 Patented July 19, 1966 3,261,470 SCREENING APPARATUS Herman I. Daniels, Rte. 2, Box 203, Bluefield, W. Va. Filed May 31, 1963, Ser. No. 284,473 8 Claims. (Cl. 210-406) This invention relates to a screening apparatus and particularly to an improved screening apparatus for separating liquid from coal fines when slurry (mixture of liquid and fines) is fed to a screening deck.

The preparation of coal and the milling of minerals is a problem today because of the increased amounts of slurries due to the increased preparation of fines. Fines are that portion of raw or processed mineral which are not considered coarse. It is known that the processing of the fine fraction is more diificult than the processing of the coarse fraction. The mixture of fines with water results in a slurry or a pulp or a sludge. The handling of the slurry is a problem because in order to obtain a product of the solid fine particles, it is necessary to dewater and dry the solid particles. The drying of the fine particles is accomplished by natural settling basins, thickening tanks, mechanical thickening such as centrifugal devices, pressure filtration, thermal drying and by natural dewatering through openings in a screen. The last method passes slurry over a screen on which the fines remain and the water drops through. A vibrating screen has been used because the vibration clears the screening surface. There are a number of disadvantages in using the vibrating screen in that the equipment is more expensive because all the structural elements must withstand the heavy vibration and during the vibration the finer particles and water are moved further from the screening surface and the coarse particles remain close to the screening surface. The exact opposite is desirable so that the water may pass through the screen. For these reasons the trend has been to return to stationary screening surfaces.

Stationary screens at a given slope angle are not able to give maximum dewatering efliciency particularly when the slurry feed rate is increased or the ratio of solids to water is changed during a feeding operation. For example, the maximum dewatering would occur only when the screen is in a horizontal position or near a horizontal position. The horizontal position or a small slope angle will cause the fines to cake or back up as the feed rate is increased or the solids to water ratio is increased. The backed-up condition is due to (i) the high viscosity of fines when the Water leaves the particles; (ii) to an increase in feed rate of the solids content to the screening portion. When the fines are backed up on-the screen, slurry with a low viscosity passes freely over the caked or backed-up fines on the screen, with a minimum of dewatering.

My invention overcomes the disadvantages of a vibrating screen or a stationary screen and gives maximum dewatering efficiency with any sudden change in solids to liquid ratio coupled with any sudden change in feed rate. This is done by making the slope angle of the screen a function of the build up of fines on the screen. The slope angle of the screen can dynamically change to a greater slope angle and back to the initial slope angle either continuously or intermittently depending upon the rate of fines build up on the screen. Thus, the critical angle of the screening surface is maintained over a period of time producing maximum efiiciency of dewatering. The critical angle is the static angle which will give maximum dewatering or maximum screening efiiciency at a steady flow of slurry with a constant ratio of solids to water. The initial slope angle in my invention is usually less than the critical angle but over a period of time because of the continual changes in slope angle the critical angle is the average angle that is achieved over any given period of time.

The present invention has solved the disadvantages of the prior art by providing; a screening surface which need not be shaken or vibrated, a screening surface requiring only simple supports which are not destroyed by vibration or subject to vibration, a screening surface which has a variable slope angle, a screening surface which is varied continuously or intermittently between an angle beyond the critical point for separation of liquids from solids and an angle within the critical angle for the proper discharge of solid fines.

I provide an apparatus for separating liquid from slurry fines and for separating slurry fines into two fractions, one even finer than the previous (e.g., the separation of minus 48 mesh fines from the original by 0 feed), comprising flow feeding means directing the flow of slurry to a downwardly sloped screening means the slope angle of which is variable, motor means to rapidly vary the said slope angle, sensing means responsive to a build up of fines on said screening means, said motor means being activated by said sensing means thereby causing said slope angle to rapidly vary through a multiplicity of angles and return to initial slope angle permitting fines tobuild up again.

The slurry is fed to the apparatus by large ducts whichare connected to a reservoir. The reservoir is bafiled so that the overflow from the reservoir is at an even rate and distributed along the top edge of an adjoining screen.

The screen is pivotally suspended from the bafiled reservoir which permits variations in slope angle determined by an intersection between the screen deck and ahorizonof said arm is pivotally connected to the screen deck structure. When the disc makes one complete revolution, the slope angle formed by the screen deck passes from the initial slope angle to a higher slope angle then back to the initial slope angle. The slope angles through which the screen passes can be changed by placing the pivotal arm in suitable positions along the disc.

When slurry is fed through the ducts, and out of the bafiled reservoir into the screening deck, Water goes through the screen and dewatered fines pass onto a collecting means. However, when the flow of slurry is increased suddenly and/ or the solid to water ratio increases, the fines on the screen begin to back up until a near solid wall of slurry is on the screen deck. In order to sense this build up, a photoelectric beam is directed through the screen. When the beam is broken, the motor is activated and the disc makes one complete revolution thereby rapidly increasing the slope angle of the' screen deck and unloading the fines onto the collector means and returning the screen deck to the original slope The screening deck has iso-bars generally spaced side by side which form the screen element and a screen deck wall is on both sides to prevent the slurry fines from spilling off the edge of the screen deck.

Directly under the screen is a water catch basin which is integral to the screen deck superstructure and moves with the screen deck when the eccentric disc is rotating.

Other details, objects and advantages of the invention will become apparent as the following description of a present preferred embodiment thereof proceeds.

In the accompanying drawings I have shown a present preferred embodiment of the invention in which FIGURE 1 is a front elevation view showing the feeding means and screen deck;

FIGURE 2 is a side elevation view showing the baffled feeding means, screen deck walls, photoelectric sensing means, motor means, arm means and alternate timing means;

FIGURE 3 is an isometric sketch showing the same structure as FIGURE 1 with parts cut away.

Referring to the drawings we have illustrated a screening apparatus which shows input ducts 12 and 13 in which slurry is fed to the reservoir housing through input ports 17 and 18. The reservoir housing 10 having an input baffle wall 14 and reservoir bafile wall 15 to assure a steady and transversive How of slurry down guide wall 16 through reservoir output 19 onto heavy duty screen banking board 20. The slurry passes onto screening deck 11 and passes over iso-bars 37 guided by screen deck walls 22. Integral to screen deck 11 is the water catch basin which catches water passing through iso-bars 37. The solid fines pass through a discharge port 26 and the water from the water catch basin 25 passes through water discharge port 27.

A suitably positioned photoelectric means comprising a photoelectric emitter 36 and a photoelectric collector 35 senses a build up of fines on iso-bars 37. When the beam of light passing from the photoelectric emitter 36 to photoelectric collector 35 is broken, gear motor 33 is activated by a suitable electric circuit between collector 35 and gear motor 33. Gear motor 33 has rigidly attached on drive shaft 32 a disc 30. Arm 29 is pivotally attached to bracket 28 and pivotal connection 31 on the disc 30. When the beam of light between the photoelectric emitter 36 and the photoelectric collector 35 is broken by the fines backing up on screen deck 11, gear motor 33 is activated thereby making one complete revolution and causing the slope angle 23 to go from fixed initial angle to a maximum slope angle back to an initial slope angle 23. To enable the screen deck 11 to pivot freely, it is attached to reservoir housing 10 through anchor plates 38 which are integral therewith by pins 24 through plates 21 integral to screen deck walls 22.

In lieu of using photoelectric emitter 36 and collector 35 as a sensing means, timing device 34 may be calibrated to a build up of fines and used to activate through a suitable circuit gear motor 33.

While I have shown and described a present preferred embodiment of the invention, it is to be distinctly understood that the invention is not limited thereto but may be otherwise variously embodied within the scope of the following claims.

I claim:

1. Apparatus for separating liquid'from slurry fines, comprising flow feeding means directing the flow of slurry to a downwardly sloped planar screen having one end pivotally connected to the flow feeding means, the slope angle of which is variable, motor means to rapidly vary the said slope angle to discharge fines accumulated on said screen, motor activating means, said motor means being activated by said motor activating means thereby causing said slope angle to rapidly vary through a multiplicity of angles and return to initial slope angle permitting fines to build up again on said screen.

2. Apparatus for separating liquid from slurry fines, comprising flow feeding means directing the flow of slurry to a downwardly sloped planar screen having one end pivotally connected to the flow feeding means, the slope angle of which is variable, liquid collector means under said screen, motor means to rapidly vary the said slope angle to discharge fines accumulated on said screen, motor activating means, said motor means being activated by said mot-or activating means thereby causing said slope angle to rapidly vary through a multiplicity of angles and return to initial slope angle permitting fines to build up again on said screen.

3. Apparatus for separating liquid from slurry fines, comprising fiow feeding means directing the flow of slurry to a downwardly "sloped planar screen having one end pivotally connected to the flow feed means, the slope angle of which is variable, motor means to rapidly vary the said slope angle to discharge fines accumulated on said screen, said motor means and said screen being pivotally connected by arm means, motor activating means, said motor means being activated by said motor activating means thereby causing said slope angle to rapidly vary through a multiplicity of angles and return to initial slope angle permitting fines to build up again on said screen.

4. Apparatus for separating liquid from slurry fines, comprising flow feeding means directing the flow of slurry to a downwardly sloped screening means the slope angle of which is variable, motor means to rapidly vary the said slope angle, said motor means driving a disc, said disc and said screening means being pivotally connected by arm means, said pivotal connection on said disc being adjustable from center to outer circumference thereby varying the rate of change of said slope angle as said disc rotates, motor activating means, said motor means being activated by said motor activating means thereby causing said slope angle to rapidly vary through a multiplicity of angles and return to initial slope angle permitting fines to build up again on said screening means.

5. Apparatus for separating liquid from slurry fines, comprising flow feeding means directing the fiow of slurry to a downwardly sloped screening means the slope angle of which is variable, motor means to rapidly vary the said slope angle, sensing means responsive to a build up of fines on said screening means, said motor means being activated by said sensing means thereby causing said slope angle to rapidly vary through a multiplicity of angles I and return to initial slope angle permitting fines to build up again on said screening means.

6. Apparatus for separating liquid from slurry fines, comprising flow feeding means directing the flow of slurry to a downwardly sloped screening means the slope angle of which is variable, motor means to rapidly vary the said slope angle, photoelectric means positioned on both sides of said screening means and transverse of said screening means, said photoelectric means casting beamed light energy between said photoelectric means, whereby said beam is broken when fines build up on said screening means, said motor means being activated when said beam is broken thereby causing said slope angle to rapidly vary through a multiplicity of angles and unload said fines and then return to initial slope angle permitting fines to build up again on said screening means.

7. Apparatus for separating liquid from slurry fines, comprising flow feeding means directing the flow of slurry to a downwardly sloped screening means the slope angle of which is variable, motor means to rapidly vary the said slope angle, timing means calibrated to a build up of fines on said screening means, said motor means being activated by said timing means thereby causing said slope angle to rapidly vary through a multiplicity of angles and return to initial slope angle permitting fines to build up again on said screening means.

8. Apparatus for separating liquid from slurry fines, comprising flow feeding means directing the flow of slurry to a downwardly sloped screening means of iso-bars spaced generally side by side, said screening means angularly disposed adjacent to said feeding means producing a slope angle which is made variable by pivotal connection means between screening means and feeding means, motor means to rapidly vary the said slope angle, sensing means responsive to a build up of fines on said screening means, said motor means being activated by said sensing means thereby causing said slope angle to rapidly vary through a References Cited by the Examiner UNITED STATES PATENTS Sackett 209-352 X Bevard 209-260 X Albrecht 209260 X Goldman 210-391 X Jauhola 2l0-391 multiplicity of angles and return to initial slope angle 10 REUBEN FRIEDMANPrimary Examiner D. M. RIESS, Assistant Examiner.

permitting fines to build up again on said screening means. 

1. APPARATUS FOR SEPERATING LIQUID FROM SLURRY FINES, COMPRISING FLOW FEEDING MEANS DIRECTING THE FLOW OF SLURRY TO A DOWNWARDLY SLOPED PLANAR SCREEN HAVING ONE END PIVOTALLY CONNECTED TO THE FLOW FEEDING MEANS, THE SLOPE ANGLE OF WHICH IS VARIABLE, MOTOR MEANS TO RAPIDLY VARY THE SAID SLOPE ANGLE TO DISCHARGE FINES ACCUMULATED ON SAID SCREEN, MOTOR ACTIVATING MEANS, SAID MOTOR MEANS 